Discharge for grinding mills



May 4, 1937. s. L. MILLER ET AL DISCHARGE FOR GRINDING MILLS Filed Sept.9, 1935 Z'Sheets-Shegt 1 INVENTORS amp/(s L. N/A LEE GEOPG'E TJol/Ms onATTORNEY.

y 1 s 1.; MiLLER ET AL 2,079,221

DISCHARGE FOR GRINDING MILLS Filed Sept. 9, 1935 v 2 Sheets-Sheet 2INVENTORS STAR/($1.. M/LLE/e BY 650205 TJo A/so/v ATTORNEY;

Patented May 4, 1937 UNITED STATE niscnnnen FOR cnmnnve Mints- Starks L.Miller and George T. Johnson, Denver,

0010., assignors to American Ball-Mill Company, Denver, Colo.

Application September 9; 1935, Serial l lo- 39,763

3 Claims.

This invention relates to improvements in grinding'mills of the typeusually referred to as ball mills, and has reference more particularlyto an improved discharge. a

It is the object of this invention to produce a ball mill of suchconstruction that eflicient grinding-either wet or dry can be effectedwith a comparatively small number of attrition members and a smallquantity of ore.

Another object of this invention is to produce a discharge of suchconstruction that the material will be subjected to a separating action,and which passes the material below a certain size to the dischargetrunnion, while the oversize material is returned to the mill-at or nearits center of rotation.

A still further object of the invention is to produce a grinding mill ofthe ball type in which the inner end of the discharge trunnion shall beso constructed that it will impart to any attrition 'memberthat comes incontact therewith, a force 7 that tends to direct it inwardly into thecenter of the mill.

' The above and other objects that may become apparent as thedescription proceeds are attained by means of a construction and anarrangement of. parts that will now be described in detail, andreference for this purpose will be had to the accompanying drawings inwhich the invention has been illustrated in its preferred form, and inwhich- I Figure 1 is a section taken substantially along line l-| Figure3, parts being broken away to better disclose the construction;

Figure 2 is a fragmentary section taken on line 2--2, Figure 1;

Figure 3 is a section ure 1;

Figure 4 is a section taken on line 4-4, Figure 3; and a Figure 5 is adiametrical section, similar to that shown in Figure 3, but which showsthe discharge arranged to feed into a tandem mill.

In the drawings, reference numeral 6 desighates the shell which isusually cylindrical, and

taken on line 3-3, Fignumeral l designates the head at the discharge:

I end. Head I is provided with a discharge trunnion 8 which is mountedfor rotation on a bearing 9, and whose upper surface is protected by acover ID. The outer end of trunnion 8 is provided with a flange -l Iwhich'cooperates with a similar flange l2 carried by the trunnion lineri3.

The flanges H and I2 are usually connected by bolts M. The liner 13 fitsthe cylindrical opening in trunnion 8, and projects into the interior ofthe mill a considerable distance. The I inner end of the trunnion lineris separated from the outer frusto-conical portion thereof by a wall l5that, inthe example shown, is provided with several sector-shapedopenings I6 which are connected by curved passages H with correspondingopenings ill in the outer surface of the liner.

Openings I9, which alternate with the openings l8, are connected bypassages 20 with openings J 2| in the inner end of the liner. An annularwall 22 extends inwardly and its inner end forms the radial boundary ofopenings 2|.

Located along'the inside of the head 1 are a plurality of curvedconduits whose interior chambers have been designated by referencenumerals 23; these conduits have curved walls 24 and 25 joined by anouter wall 26 and an inner wall 21; The outer wall has an arcuateportion I 28 that fits against the inner surface of the shell 6. Wall 24has an opening which is closed by a grate 29.

As best shown in Figure 1, each wall 24 turns abruptly adjacent theopening in which the grates 29 are fitted so that each grate rangeslaterally from the remainder of wall 24. This arrangement is effectivefor retaining some liquid against wall 24 which doesnt pass throughgrate 29 while any given conduit is in an asends of liners 33 are soconstructed that when V they are in their fixed position in the mill, in

spaced relation to the raised surfaces of liners 32, the space betweenthe aforesaid liners is narrowest adjacent the side wall of each liner33 in the forward position with respect to the direction of rotation,and progressively widens rearwardly to the opposite side wall of eachliner 33. In Figure 3 the relative positions of liners 32 and 33 havealso been shown and it will be noted that the narrowest space betweenthe'liners is nearest the inside of the mill.

From the foregoing, it is apparent that if material from the mill entersthe space between the liners 32 and 33 it will not become lodged andblock the passage as the natural movement of such material is rearwardlywith respect to the direction of rotation and outwardly toward the endofthe mill, and in each of these directions thespace progressively widens.v

.The inner ends of the passages 23 are arranged in register with theopenings It in the trunnion liner and communicate with the discharge endof the trunnion liner through passages i1 and openings 8 in the mannershown in Figure 3.

It will be observed from Figure 3 that open spaces 30 are formed betweenthe walls 24 and 25 of adjacent conduits. An annular plate 3| offrusto-conical shape surrounds the inner end of the trunnion liner andis held in position thereby and rests against the walls 21.

The plate 3| is covered interiorly of the mill by end-liners 33 whichare mounted on and surround the inner periphery of the lining and boththe plate 3| and the liners 33 are spaced from the interior liners 32 ofthe shell 6 of the mill,

which are supported on channeled girders I32. The space between theend-liners covering the plate 3| and the shell-liners of the mill,provides an annular opening 34 through which material may enter thechambers 30.

The opening 34 is too small for the attrition members 35 to enter, andthe openings 2| should be suificiently wide to permit of a ready passageof the oversize, irrespective of the size of the attrition members whichmay be smaller than the openings. The chambers 30 are in communciationat their inner ends with the openings IS in the wall of the trunnionlining I3 so that the oversize material that enters the chambers 30 willre-enterthe mill through the passages 20 and the openings 2|.

When the mill is in operation, it rotates in a counter-clockwisedirection when viewed as in Figure 1, and the curved walls 24 serve toelevate the material, causing it to flow first over the grates 29, wherethe material below a certain size passes into the conduits 23. As themill continues to rotate, the oversize material will follow the walls 24and will finally be returned to the mill through the opening 2|, whilethe material that passes thru the grates will be delivered to thepassages i1 and will be discharged into the trunnion lining |3 thru theopenings Hi.

In Figure 3, an attrition member 35 has been indicated by dotted linesand shown as positioned in one of the openings 2|. The wall 22 serves asa barrier or deflecting member to prevent general ease of entry of thelarger attrition members and to direct the members toward the center 36which forms the extreme inner end of the trunnion lining and thecombined action of the wall 22 and the end 36 serves to direct themembers inwardly toward the center of the mill.

It will be observed from an inspection of Figure 3 that the attritionmembers and the ore form only a comparatively thin layer over thelowermost part of the inner surface of the 'mill, and by reason of thefact that the opening 34 is adjacent the inner surface of the lining 32,the ore pulp or the ore that has been ground fine enough to pass throughthe opening 34 can enter the chambers 30, where the separating action,above described, takes place, and from which the oversize is returnedfor further grinding. The ore is usually ground wet, but with themachine above described, it can also be ground dry.

In Figure 5 a tandem mill has been shown, and the rough grinding millhas been designated by A, while the regrinding mill has been designatedby B.

The two mills are separated by a wall In whieh corresponds to the head Iin Figure 3, and arranged along the left hand side of the head la areconduits 23a that correspond in every particular with those alreadydescribed, with this exception, that those above described fit against afrusto-conical head 1, while those shown in Figure 5 fit against theplane head la.

Since the material from mill A is delivered to the mill B for furthergrinding, that portion of the trunnion lining l3 that is located outsideof the wall I5 is unnecessary, and has been omitted, but-in otherrespects, the construction is the same, and the parts have thereforebeen designated by the same reference numerals.

When a tandem mill is employed, the material that passes through thegrates 29 is reground in mill B, and it is evident that as many millscan be connected in tandem as desired.

One of the important advantages of the construction above described isthat the pulp line can be kept very low and a correspondingly smallnumber of attrition members used, and this reduces the power required tooperate the mill. The conduits, by means of which the separation iseffected, are of simple construction, and can be made withoutdifliculty, and since they are alternately duplicates, they may be madeinterchangeable and independently replaceable, or they may be made apart of the head-assembly.

Having described the invention, as new is:

1. In a grinding mill mounted for rotation and having a head providedwith a discharge opening, a hollow liner in the opening, the end of theliner projecting beyond the inner surface of the head, the liner havinga plurality of passage ways from the periphery to one end and aplurality of passages leading in a reverse direction to a commonopening, which latter opening extends to the other end of thecylindrical liner, a plurality of radially extending conduits locatedadjacent the inner surface of the head with their inner ends incommunication with the passages in the liner that open outside of themill, the walls of the conduits on the sides facing in the direction ofrotation having openings forming a grate, the spaces between theconduits communicating with the passages in the liner that open withinthe mill, a removable cover forming an inner wall for the spaces, thecover terminating a short distance from the inner periphery of the millwhereby openings are provided between the interior of the mill and theouter ends of the spaces between the conduits, and through whichmaterial may enter said spaces when the mill rotates.

2. In a grinding mill mounted for rotation, and having a head providedwith a central discharge opening, a cylindrical liner in the opening,the end of the liner projecting beyond the inner surface of the head,the liner having a plurality of passage ways from the periphery to oneend and a plurality of passages leading in a reverse direction to acommon opening, which latter opening extends to the other end of thecylindrical liner, a plurality of separate curved conduits 10- catedadjacent the inside surface of the head and radially arranged, the innerends of the conduits communicating with the passages in the what isclaimed liner which open on the outside, the spaces beform" chambers;connected: at inner and their outer ends-with the interior'oi the mill.

3. A grindingmill comprising: a shellahavinz, one end closed bygaa headprovided with a hollow discharge trunnion} a liner im the trunnion, oneend of the linerextiending' into; the mill, the liner having atransverse partition, intermediate its ends, the inner end 0! the linerhavinga. pm

rality oi passages. alternate passages extendingirom the periphery tothe outside of the transverse partition and the others extending fromthe periphery to the inside of the mill; a plurality of separateradially extending conduits having their inner ends in communicationwith the pasconduit-walls on. the side facing in sagesv that. open onthe; outside of the mill, the the. direction 01' rotation havingopenings forming a: grating, means rforhoiding theeonduits from movingrela- 'tive to each other and. relative to" the head, a removable cover:for. the; spaces between the conduits, theinner.- ends of the spacesbetween the conduits being in communication with the. pascages in" theliner that open within the mill, there being" openings from the interiorof the mill to the spaces between the conduits, said openings beingadjacent the inner periphery oi'the mill.

STARKB L. MILLER. GEORGE '1. JOHNSO

